February 20, 2015

Cold Air Mining

By Caimin McCabe

With the ever increasing focus on new technology to improve environmental performance, people sometimes forget how effective old technology is.  An example of this is the use of Thermal Labyrinths, which can offer significant passive conditioning benefits.  Labyrinth’s can offer 8-10°C pre-cooling of outside air in the height of summer and 6-7°C pre-heating in winter.  However, their effective integration requires a different design and control logic to that used for traditional air conditioning systems in particular with respect to purging.

I have integrated thermal labyrinths in a wide range of buildings, ranging from schools, offices and university buildings to great success.  One such development that has taken advantage of this “old” technology is the Gungahlin College project.

Gungahlin College, Australian Capital Territory (ACT)

The Gungahlin College project involved the construction of a mix of educational and community facilities in an integrated campus, including a secondary college to accommodate 900 year 11 and 12 students, a Learning Centre for the Canberra Institute of Technology (CIT), as well as a shared Library, Performing Arts Theatre, and Town Park for the Gungahlin Community, in the new suburb of Canberra.

The challenge for the project was to maximise the climatic and environmental responsiveness of the development while at the same time meet the highly variable usage patterns and user expectations.  An example of this was the Department of Education & Training’s philosophy schools should not be air conditioned. Whereas facilities shared with the general public – such as the Library, Performing Arts Theatre and the tertiary facility had expectations of air conditioning.

The variety of uses within the development, their different hours of use as well as the strong environmentally response sought – led to the idea of a central thermal labyrinth or passive infrastructure being implemented as part of the overall environmentally responsive solution.

To suit the structural design solution adopted to address the step in the site the thermal labyrinth was integrated below the paved courtyard between the Library / CIT building and the Secondary College building.

The central location of the thermal labyrinth allowed its benefit to be maximised to serve the Secondary College during school hours, the Library / CIT building in the evening, weekends and school holidays, and the theatre at night.  The labyrinth was designed to provide up to 9°C passive cooling under design summer conditions and 7°C passive heating in winter.

The passive infrastructure approach of the thermal labyrinth provides a shared resource to the different parts of the development, and offers a number of predicted benefits including:

  • Passive comfort control within the learning hubs of the school during the summer without the need for active cooling and pre-heating in winter. It also provides 100% outside air ventilation all year round for improved IEQ, as well as enhances the effectiveness of the natural stack ventilation strategy adopted within the school.
  • A 30 per cent reduction in carbon emissions associated with heating and cooling of outside air required for the library and CIT spaces during library operating hours.
  • A 46 per cent reduction in carbon emissions associated with heating and cooling of outside air required for the theatre.

I would welcome hearing other peoples’ experience with the integration of thermal labyrinths or other ‘old’ technologies that should have greater use.

Find out more about Cundall – http://www.cundall.com/

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Building Services Engineering, Caimin McCabe, Sustainable Design

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